Process for coating drawn metal parts

ABSTRACT

Process for using coating guns to apply a conductive layer to the inside of battery cans moving on a conveyor with intermittent move and dwell times. Pats are automatically inspected. If a layer is defective due to a disabled coating gun, the process includes firing another coating gun at twice its normal firing rate and/or shifting its position so that it does the job of two coating guns.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of provisional applicationSerial No. 60/437,531 filed Dec. 31, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a high volume manufacturing process forcontinuously coating and inspecting drawn metal parts as part of acontinuous series of operations to produce finished drawn metal parts.An example of high volume manufacturing of drawn metal parts is theproduction of battery cans, which are used as the primary battery casingfor commercial cells, such as A, AA, AAA, C, D, F, M, etc.

[0003] Manufacturing of battery cans according to the prior art isgenerally accomplished by a batch and queue process in the followingmanner. A redraw press accepts narrow strip stock from a payoff reel andperforms blanking, cupping and subsequent redraw operations. The entirebattery can is manufactured in each stand-alone redraw press and thecans are collected in bulk in containers. The press operator and/ortoolmaker manually inspect the dimensional and cosmetic attributes ofthe can. A pre-determined number of cans are removed randomly andinspected. Next the containers of parts from the press are moved to astaging area near a washer/dryer machine. The washer/dryer, whichremoves the drawing lubricant, is typically a rotary bulk washer with acob dryer. An operator feeds the cans into the inlet of the washer. Thewashed cans are caught in bulk hoppers or cartons.

[0004] Next the washed cans are moved to a staging area near a coatingmachine. The coating machines apply thin film of coating material to theinterior of the can. The cans are dried in bulk in a curing oven. Anoperator feeds the cans to the coaters. The cans are inspected forproper coating and then placed into the final packaging containers.

[0005] The batch and queue process described above has severaldisadvantages. The narrow strip stock produces significant scrap, due tounusable material at the edge of the strip. The required coil changes tofeed the narrow strip stock to the redraw press lead to inefficienciesin operation. Damage can occur due to parts contacting other parts inthe batch containers. Rejection of parts due to dimensional, coating andcosmetic defects may be inconsistent due to using different inspectors.

[0006] Another disadvantage is the requirement to follow the partsproduced by a particular tool through the manufacturing process bykeeping track of the batch container corresponding to each tool. This isnecessary in order to halt operation from a particular redraw press andtake corrective action if dimensional changes occur due to tool wear.Manual operator time is required to move batch containers from oneoperation to the next while retaining identification of the batch withthe tool producing the part.

[0007] Accordingly, one object of the present invention is to provide acontinuous high volume process for coating and inspecting the coating ondrawn metal parts.

[0008] Another object of the invention is to provide an improvedcontinuous process for tracking drawn metal parts through coatingoperations so as to identify the coating gun that coated the parts.

[0009] Still another object of the invention is to provide an improvedprocess for inspecting coated parts and taking corrective action to shutdown the coating gun if the coating is defective.

[0010] Another object of the invention is to provide an improved processfor coating and inspecting the coating on drawn metal parts, andsubstituting additional coating guns if a coating gun is defective.

SUMMARY OF THE INVENTION

[0011] Briefly stated, the invention concerns a process for coating andinspecting drawn metal parts, comprising the steps of: providing asingle ordered stream of drawn metal parts having a repeating sequentialorder, said repeating sequential order enabling identification of thedrawn metal part by the location of the drawn metal part in said orderedstream; conveying said ordered stream with continuous movement of thedrawn metal parts; converting the movement of the ordered stream into anintermittent motion having a move time and a dwell time; providing aplurality of coating guns; coating pre-selected portions of a selecteddrawn metal part during a first dwell time with a first coating gun;providing automatic inspection means for determining if the coating isdefective; inspecting the coating of said selected drawn metal part withsaid automatic inspection means during a second dwell time; shuttingdown said first coating gun if the coating is defective, said selectedcoating gun being identified by the location of the removed drawn metalpart in the ordered stream; and enabling a second coating gun to coatdrawn metal parts in the same sequential location in the ordered streamthat was previously assigned to the first coating gun. The enabling stepis preferably carried out by firing the second coating gun at twice itsnormal firing rate, including shifting the position of the secondcoating gun in some cases.

DRAWING

[0012] The invention will be better understood by reference to thefollowing description, taken in connection with the accompanyingdrawing, in which:

[0013]FIG. 1 is a simplified block diagram of the manufacturing process,

[0014]FIG. 2 is a schematic representation of a merge and sequencemachine,

[0015]FIG. 3 is a schematic representation of portions of a conveyor,with means to remove a part for inspection,

[0016]FIG. 4 is a schematic representation of apparatus used to coatdrawn metal parts,

[0017]FIG. 5 is a schematic diagram of the packing process, and

[0018]FIG. 6 is a perspective view of a computer generated model showingthe actual placement of equipment, with simplified diagram of theprocess computer controls.

GENERAL DESCRIPTION OF THE PROCESS

[0019] Referring to FIG. 1 of the drawing, a coil payoff system 10 feedsa cupping press 12 with a wide strip of thin metal from a coil. Cuppingpress 12 performs a blanking and drawing operation to produce seven cupsat a stroke, which are fed onto a magnetic conveyor 14. The flow ofparts from the cupping press 12 divide into two “cells” A and B. Eithercell A or B may operate independently of the other throughout much ofthe manufacturing process, even though they rejoin to share someequipment toward the end of the process.

[0020] Conveyor 14 supplies the cups to redraw presses 16, 18 in cell Aand to redraw presses 20, 22 in cell B. In order to provide for possibledowntime of cupping press 12 and/or redraw presses, part accumulators24, 26 act as buffers to receive or discharge cups as necessary.Accumulators 24, 26 are towers with helical tracks for temporary storageof parts with control means to switch parts to the presses if thecupping press is not operating, but any type of storage capable ofaccumulating and discharging parts via conveyors will be suitable.

[0021] The redraw presses 16, 18, 20, 22 each are equipped with at leasttwo sets of redraw stations, hereinafter defined “tools”. As defined inthis patent application, a “tool” (singular) is actually a setcomprising several redraw punches and dies, which successively draw thecups into the final dimensional shape of a battery can and cut off thetop rim of the can. Thus, in the illustration shown, each press handlestwo “tools” and, therefore, produces two parts during each stroke.However, more than two tools per press are also possible.

[0022] Battery cans from each of the tools in each of the redraw pressesare discharged onto a separate conveyor, such as that indicated byreference number 28. Means are provided to remove a sample for localinspection as shown at 30. While a single conveyor 28 and its inspectionstation 30 are indicated on the drawing for tool number four of redrawpress 18, a similar arrangement is placed at the tool discharge of eachredraw press. If there are more than tools in each redraw press,additional conveyors will be required, one for each tool.

[0023] Battery cans 1, 2, 3, 4 from presses 16, 18 in cell A areseparately accumulated in four serpentine tracks, one for each tool, inan accumulator 32. Similarly battery cans 5, 6, 7, 8 from redraw presses20, 22 in cell B are separately accumulated in four serpentine tracks inaccumulator 34.

[0024] A special ordered merge device 36 in cell A and an identicaldevice 38 in cell B perform an ordered merge operation to be describedlater in detail. Briefly the separate streams of parts from the tools ofeach of the presses are merged into a single ordered stream of partsmaintaining a sequential order that enables identification of the toolby the location of the part in the stream. This ordered stream of partsis represented by the dashed lines 40-42 representing the conveyors fromthe ordered merge 36, 38.

[0025] An automatic dimensional inspection machine 44 is shared by bothcells A and B and equipped with instruments, which measure certaincritical dimensions in the battery cans. Part ejectors 46, 48 areprecisely controlled to remove a part from a pocket on a conveyor 40, 42and place it in the dimensional inspection equipment 44. It is importantto note that the empty pocket in the conveyor from which the part isremoved is maintained throughout the manufacturing process, so that theintegrity of the ordered stream is maintained as the battery cans movethrough the process. This integrity is maintained when parts aretransferred from one conveyor to the next.

[0026] Battery cans from cell A and cell B are conveyed to washer/dryers50, 52 respectively. There, the drawing compound is removed and thebattery cans dried. Thereafter, each washer/dryer 50, 52 supplies abuffer 54, 56 respectively. Buffers 54, 56 are maintained half-full by amoveable bridge mechanism. The buffer level controls the speed of thecoating/inspection conveyor downstream of it.

[0027] Optical camera inspection systems 58, 60 measure the streams ofbattery cans from the buffers 54, 56. The parts are fed in ordermaintaining gaps for any missing parts, onto special motion convertingconveyors 62, 64 equipped with coating guns. These devices will bedescribed further in detail, but, briefly stated, the continuouslymoving stream of parts is converted to an intermittently moving orindexed motion having a dwell time and a move time. During the dwelltime, the cylindrical battery cans are rotated while they are sprayed onthe inside with coating guns. Following the coating operation, anautomatic optical inspection system at 66, 68 inspects internal coating,and any cosmetic anomalies on the exterior of the battery can. Rejectsare automatically removed by part ejectors 70, 72. The parts, stillsegregated in the respective conveyor pockets for the two cells A, Bmove to a coating dryer 74 and, from there, to the pack operationindicated at 76.

Ordered Merge Operation

[0028] While the preceding section describes the overall process formanufacturing drawn metal parts in a general discussion, several aspectsof the process will be described in detail. One of these is the orderedmerge operation, which combines the separate streams of parts from theseparate drawing press tools in such a way that the sequence is alwaysthe same and is repeated periodically. In this way, the segregatedstream of parts are merged into a single ordered stream of drawn metalparts having a sequential order which enables identification of thedrawing press tool in which the part was made.

[0029]FIG. 2 illustrates in simplified diagrammatic fashion the orderedmerge operation. It will be understood that the actual configurationwill vary according to size and type of the parts, as well as variationsin the components. The ordered merge machine is shown generally at 80and comprises four separate accumulating receptacles 82, 84, 86, 88.These are part of the accumulators 32 or 34 shown in FIG. 1. Each suchaccumulating receptacle receives drawn metal parts from a differenttool, in this case parts 1, 2, 3 and 4 coming from tool one, tool two,tool three, and tool four respectively of presses 16, 18 (FIG. 1).Whenever parts 1, 2, 3 and 4 are depicted in the following drawings,they are deemed to be from their corresponding source tool, althoughthey may appear at different places in the processes to be described.Accumulating receptacles 82, 84, 86, 88 supply feed wheels 90, 92, 94,96 respectively. The feed wheels supply parts to a merge wheel 98 whichfeeds a conveyor 100. The feed wheels have pockets, such as 102, and themerge wheel 98 has pockets, such as 104. The feed wheels aremechanically geared to the merge wheel, so that a pocket 102 on an feedwheel registers with every fourth pocket 104 on the merge wheel as thewheels turn.

[0030] If there are more than two tools on each redraw press, e.g.,three tools, the feed wheels and index wheels must be modifiedaccordingly to include the proper number of pockets.

[0031] Conveyor 100 is designed to have a carrier belt 106, withdividing walls 108 providing segregated pockets 110. The speed of theconveyor 100 is timed to coincide with the speed of the merge wheel 98,so that the pockets 104 on the merge wheel feed the segregated pockets110 on the conveyor in precise order. FIG. 2 illustrates thataccumulating receptacle 86 was temporarily empty, so that feed wheel 94was previously not feeding parts 3 to the designated pocket on mergewheel 98. Therefore the segregated pockets 110 on conveyor 100 aretemporarily empty, but the single ordered stream of parts continues toflow to the next intermediate processing operation.

Part Ejectors

[0032] The process provides for removal of parts at various points ofthe process for dimensional inspection, for local tool maker inspection,for defects located at any point in the process. Such part ejectors areshown on FIG. 1, for example, at 29, 46, 48, 70, 72. FIG. 3 illustratesschematically, in simplified form, the operation of such a part ejector.A conveyor 112 is made up of articulated links 114 hinged together atpivot points (not shown). Each such link has a divider wall 116projecting upwardly from the link platform. The space between dividerwalls 116 provides segregated pockets for the parts 1, 2, 3, 4 supportedon the platforms of the articulated links 114. The drawn metal parts arecylindrical and each has an open end 118, as is typical of battery cansand similar drawn parts.

[0033] Removal of parts is accomplished with an air jet 120 having a tip122 aligned with the open end of the parts, and a collection tube 124having an open end 126 aligned with the axis of the air jet. Thecollection tube is provided with directed openings 128 which are, inturn, surrounded by a manifold 130. When it is desired to remove a part,air jet 120 and manifold 130 are supplied with a blast of high pressureair, pushing the part 3 into the open end 126 of the collection tube124. Air entering the manifold 130 and openings 128 propels the part 3through the tube to a collection point (not shown).

[0034] This arrangement is known as a “bazooka”, and may be eitherautomatically or manually actuated to remove a part from a segregatedpocket. Since the parts are in sequence, the part corresponding to anyselected tool source may be removed. The location of the pocket on theconveyor is a function of the conveyor speed which is precisely known byan encoder, and controlled by a programmed logic computer (see FIG. 6).

Coating Operation

[0035] Referring to FIG. 4 of the drawing, a conveyor 132 is providedwith a known type of mechanism (not shown) to convert a continuousmovement to an indexed movement having a move time and a dwell time. Thecoating operation involves spraying a conductive coating into the openends of the drawn metal parts. Coating is accomplished by means ofcoating spray guns A, B, C, D. These are spaced along conveyor 132,which is moving from left to right in the drawing, so that each spraygun is automatically actuated to spray a jet of coating material intothe open end of the part during the dwell time of conveyor 132. Rotatingapparatus (not shown) is also provided to rotate the cylindrical partsabout their axis while the spray gun is active so as to obtain a uniformcoat. Spray guns A, B, C, D are spaced along conveyor 132, so thatcoating gun A coats the inside of part 1, coating gun B coats the insideof part 3, coating gun C coats the inside of part 4, and coating gun Dcoats the inside of part 2.

[0036] Because of the possibility that one or more coating guns maybecome inoperative, a unique system is employed to enable a coating gunto take over the job of an inoperative coating gun, while continuing toprocess its previously assigned part. The coating guns are capable offiring twice as fast as their normal firing rate. Also, coating guns Band C are able to shift one position along conveyor 132 to the alternaterespective positions indicated by reference letters B′, C′.

[0037] Method 1: If gun B should become inoperative, it will be observedthat coating gun A may be operated at twice its normal firing rate tocoat parts 1 and 3. Similarly, gun B may take over for gun A should gunA become inoperative. In a similar manner, guns C and D may assume theduties for each other by firing at twice the normal rate.

[0038] Method 2: Should both guns C and D become temporarilyinoperative, gun B may be shifted to position B′. With both guns A andB′ firing at twice the normal rate, they can take over the job ofcoating all four parts. In a similar manner if both guns A and B becometemporarily inoperative, gun C may be shifted to C′ and guns C′ and D,firing at twice the normal rate will coat all four parts.

[0039] The coated parts are inspected by an optical inspection system134 and removed by a parts ejector 136 if they should be unacceptable.

Packing Segregated by Tool

[0040] Referring to FIG. 5 of the drawing, a packing area showngenerally as 138 receives an ordered stream of parts 1, 2, 3, 4 on aconveyor 140 from cell A and a second ordered stream of parts 5, 6, 7, 8on a conveyor 142 from cell B. In keeping with the philosophy of theinventive process, some of the pockets of the conveyors may be emptybecause of removal of parts upstream for various purposes. A series ofreceptacles 144 are provided, each one from a different tool. A U-shapedconveyor 146 carries boxes of parts from a box filling area showngenerally as 148 to a box collection area shown generally as 150.

[0041] Empty boxes are supplied along a first table (or conveyor) 152.Boxes being filled are stationed along a second table (or conveyor) 154and, when full, are pushed onto conveyor 146. The filled boxes are thenconveyed to a specific collection station, such as the one designated at156. From there they are removed for shipment, the boxes being coded todesignate the source tool from which they were manufactured.

Dimensional Test Unit

[0042] Referring to FIG. 1 of the drawing, dimensional inspection iscarried out by dimensional test unit 44. This unit is designed tomeasure, via touch probes, pre-defined dimensions on the parts. The unitwill measure parts from eight tools plus allowance for manualinsertion/inspection of parts. The unit provides for measuring, indexingand discharge of parts. A detailed description of the device as used tomeasure that parts is beyond the scope of this application. However,such devices are known in the prior art. Part ejectors such aspreviously mentioned in connection with FIG. 3 are attached to conveyorsfeeding the washer/dryers 50, 52, as indicated at 46, 48 in FIG. 1. Theparts are introduced vertically, closed end down. An electromagneticbrake holds the part momentarily, and then releases the part into thepocket in the dimensional test unit 44. When the dimensional test unitis in automatic mode, parts are requested for dimensional measurement ina pre-selected sequence. A signal is received from an encoder on theconveyor informing it that the requested part is positioned in front ofthe part ejector. The part ejector is activated and the part enters thedimensional test unit.

[0043] The dimensional test unit measures a part approximately every 10seconds. If eight tools are running, there will be an 80 second delaybetween the time a part is measured and the time a part from the sametool is measured again. If a defective part is detected, a second partfrom the same tool should be requested as soon as possible to verify theoriginal result. Since the line is continuing to move, there could be aconsiderable number of defective parts downstream, as well as thoseupstream from the defective tool. The dimensional test unit sends theappropriate signals to stop the press with the defective tool, to stopthe discharge conveyor from the appropriate buffer 54, 56, and toactivate appropriate parts ejectors to purge the line of all parts fromthat tool, both upstream and downstream. Corrective action on thedefective tool may then be taken, while the line continues to run,maintaining empty pockets corresponding to those pre-selected for thatparticular tool.

Process Speed Control

[0044] The manufacturing system includes various safeguards and controldevices to maintain production of drawn metal parts in an optimummanner, and maximize overall production, while assuring that failure ordefective operation of any piece of equipment does not shut down theentire line. Reference to FIG. 6 shows a perspective view of the actualconfiguration of the production line. Only cell A is indicated on thedrawing, along with apparatus that is shared by cells A and B. Thereference numbers of the pieces of equipment correspond to those inFIG. 1. A programmed logic computer 158 is representative of one or moreprogrammed logic computers receiving signals and sending commandsrepresented by phantom lines. Any deficiency in cups from the cuppingpress that is detected at 160 is communicated over lines 162 to controlsfor the spiral tower buffer 24 to augment the supply. Shortage of partsin the buffer 24 signals cupping press 12 over line 164.

[0045] Press strokes per minute of the four redraw presses are detectedand communicated to PLC 158 over lines 166, 168. Press stroke speeds areused in a computer program to set the speed of washer/dryer 50 overcontrol line 170. The speed of the discharge from buffer 54 and thewasher/dryer discharge is set to vary in accordance with the capacitylevel of the buffer, speeding up as the buffer level of parts lowers andslowing down as it fills up. This is indicated by control line 172. Themerge wheel for ordered merge unit 36 is directly driven by the washer50. Any back-up of parts into the separately fed accumulators 32 isdetected at 174 and shuts down the appropriate press. The coating linesand their associated conveyors 62 are controlled by the speed of thedischarge conveyor from buffer 54, as indicated by control line 176.

[0046] Therefore, it can be seen that by provision of appropriateaccumulators and buffers at various stages in the process, as well ascontrolling the conveyor speed of intermediate upstream or downstreamprocessing units, the continuous in-line process can continue to operateat optimum speed. This is despite the removal of parts at various pointsin the process for inspection or due to faulty manufacture.

[0047] Other modifications of the invention will become apparent tothose skilled in the art and it is desired to cover in the appendedclaims all such modifications as fall within the true spirit and scopeof the invention.

1. Process for coating and inspecting drawn metal parts, comprising thesteps of: (a) providing a single ordered stream of drawn metal partshaving a repeating sequential order, said repeating sequential orderenabling identification of the drawn metal part by the location of thedrawn metal part in said ordered stream; (b) causing said ordered streamto move with an intermittent motion having a move time and a dwell time;(c) providing a plurality of coating guns firing at normal firing ratesduring said dwell times; (d) coating a pre-selected portion of aselected drawn metal part during a first dwell time with a first coatinggun; (e) providing automatic inspection means for determining if thecoating is defective; and (f) inspecting the coating of said selecteddrawn metal part with said automatic inspection means during a seconddwell time.
 2. The process according to claim 1, including theadditional step of (g) enabling a second coating gun to coat drawn metalparts in the same sequential location in the ordered stream that waspreviously assigned to the first coating gun if the inspected coating isdefective.
 3. The process according to claim 2, wherein said additionalenabling step (g) comprises firing the second coating gun at twice saidnormal firing rate.
 4. The process according to claim 2, wherein saidadditional enabling step (g) comprises shifting the position of saidsecond coating gun along said ordered stream and also firing the secondcoating gun at twice said normal firing rate.
 5. Process for coating andinspecting drawn metal parts, comprising the steps of: (a) providing asingle ordered stream of drawn metal parts having a repeating sequentialorder, said repeating sequential order enabling identification of thedrawn metal part by the location of the drawn metal part in said orderedstream; (b) causing said ordered stream to move with an intermittentmotion having a move time and a dwell time; (c) providing a plurality ofcoating guns operating at normal firing rates during said dwell times;(d) coating a pre-selected portion of a selected drawn metal part duringa first dwell time with a first coating gun; (e) providing automaticinspection means for determining if the coating is defective; (f)inspecting the coating of said selected drawn metal part with saidautomatic inspection means during a second dwell time; (g) shutting downsaid first coating gun if the coating is defective, said selectedcoating gun being identified by the location of the removed drawn metalpart in the ordered stream; and, (h) enabling a second coating gun tocoat drawn metal parts in the same sequential location in the orderedstream that was previously assigned to the first coating gun.
 6. Theprocess according to claim 5, wherein said additional enabling step (g)comprises firing the second coating gun at twice said normal firingrate.
 7. The process according to claim 5, wherein said additionalenabling step (g) comprises shifting the position of said second coatinggun along said ordered stream and also firing the second coating gun attwice said normal firing rate.